In ruminants, e.g., beef and dairy cattle, sheep, etc., ingested feed first passes into the rumen, where it is pre-digested by fermentation. During this period of fermentation the ingested feed may be regurgitated to the mouth where it is salivated and ruminated. After a period of fermentation, absorption of digested nutrients starts and continues in the subsequent sections of the digestive tract. This digestive process is described in detail by D. C. Church, "Digestive Physiology and Nutrition of Ruminants", Vol. 1, O.S.U. Book Stores, Inc., of Corvallis, Oreg.
The rumen serves as an important location of metabolic breakdown of ingested foodstuffs through the action of microorganisms which are present therein. Ingested food is typically retained in the rumen for from about 6 to about 30 hours, during which time it is subject to metabolic breakdown by the rumen microorganisms. When the rumen contents pass into the abomasum and intestine, the microbial mass is digested, thus providing protein to the ruminant. Thus, the natural nutritional balance of the ruminant animal is primarily a function of the microbial composition and population.
In preparing nutrients and medicaments intended for administration to ruminants, it is important to protect the active ingredients against the environmental conditions of the rumen, i.e., microbial degradation and the effects of a pH of about 5.5, so the active substance will be saved until it reaches the particular location where adsorption takes place. It is well known that the rate of meat, wool and/or milk production can be increased if sources of growth limiting essential amino acids, and/or medicaments, are protected from alteration by microorganisms in the rumen and become available for direct adsorption by the animal later in the gastrointestinal tract.
Materials which protect the core against degradation by the rumen contents should be resistant to attack by the rumen fluid but must make the active ingredient available rapidly in the more acidic fluid of the abomasum (postruminally) at a pH within the normal physiological range of about 2 to about 3.5.
Because proteins are subject to breakdown in the rumen, it has been suggested that protein-containing nutrients fed to ruminants be treated so as to permit passage without microbial breakdown through the rumen to the abomasum. Suggested procedures have included coating the protein material, for example, with fats and vegetable oils; heat treating of the protein material; reacting the protein material with various compounds such as formaldehyde, acetylenic esters, polymerized unsaturated carboxylic acid or anhydrides and phosphonitrilic halides, etc.
It is likewise well-known that some medicaments are more effective when they are protected from the environment of the rumen. See, for example, U.S. Pat. Nos. 3,041,243 and 3,697,640.
Compositions containing nutrient and medicaments for administration to ruminants must also exhibit adequate stability upon storage. In particular, such compositions must retain sufficient activity when stored in high humidity and/or heat so that the compositions will be effective for their intended purpose. In addition, such compositions must be stable when in contact with moist feed.
In accordance with the present invention, a polymeric coating having a hydrophobic substance and a flake material dispersed therein, which coating is resistant to environmental conditions of the rumen but releases the core material under the environmental conditions of the abomasum, provides a very desirable utilization efficiency by ruminants. The core material may also contain a neutralizer to provide a pH above about 5.5.
The coating material has the ability to withstand environmental conditions of the rumen, and the ability to expose the core material of the pellet in the environment of the abomasum. Thus, the coating material is resistant to pH conditions of about 5.5 for at least about 24 hours. The coating material releases the core material upon exposure to post-ruminal environmental conditions having a pH of about 3.5 after a time of about 5 minutes to about 6 hours. The exposure of the core may occur by the coating becoming permeable to the fluids therein or by dissolving or disintegrating. Another requirements for the coating material is to have the ability to withstand feed environment or storage conditions of relatively high heat and/or humidity without a significant loss of rumen-stable and post-rumen release properties.
U.S. Patents of interest includes U.S. Pat. Nos. 3,619,200; 3,880,990; 3,041,243; 3,697,640; 3,988,480; 3,383,283; 3,275,518; 3,623,997; 3,073,748; 3,829,564; 3,832,252; and 3,917,813.
Of particular interest are U.S. Pat. Nos. 4,181,708; 4,181,709; and 4,181,710. The disclosure of U.S. Pat. No. 4,181,708 is incorporated herein by reference. The '708 patent discloses rumen-stable pellets coated with a mixture of a polymeric material, a hydrophobic material, and a flake material, and the '710 patent discloses rumen-stable pellets coated with a mixture of polymeric material, hydrophobic material and inert filler. It has, however, been unexpectedly discovered that when the nutrients and/or medicaments of the core are highly water soluble (such as glucose and lysine which have a solubility of more than 60 gm/100 gm water at 25.degree. C.) excellent results are obtained when the hydrophobic material and flake material are present in amounts as described herein. In addition, it has been unexpectedly discovered that when the glass transition temperature (Tg) values of the coating compositions are as described herein, said compositions have increased stablity to heat and/or high humidity.